1. Field
Implementations described herein generally relate to semiconductor manufacturing and more particularly to a method and apparatus for delivering feedstock gases in multiple zone inductively coupled plasma reactors and the like.
2. Description of the Related Art
As the feature size of the device patterns get smaller, the critical dimension (CD) requirements of these features become a more important criterion for stable and repeatable device performance. Allowable CD variation across a substrate processed within a processing chamber is difficult to achieve due to chamber asymmetries such as chamber and substrate temperature, flow conductance, and RF fields.
A conventional inductively coupled plasma reactor has feedstock gases injected through a nozzle at the center of the dielectric window at the top of plasma reactor. The feedstock gas is injected through a metal gas line which runs underneath the coil, parallel to the dielectric window, to the nozzle located at the center of the dielectric window. This method allows for the gas to be symmetrically delivered to the reactor. However, as the metal pipe line is in the influence of a strong electromagnetic field from the coils, it develops an inductively or capacitively coupled voltage.
Traditional reactors only have gas injection at the center of the reactor. Although such reactors have robust performance histories at larger CD's, coupling of the voltage to the metal feedstock gas line during plasma processing affects the uniformity of the substrates processed in the chamber when processing state of the art small CD's. After coupling, evidence of the gas line may be printed on the substrate processing map. It is impractical to use a round hollow metal disc instead of a single gas line to deliver the gas as the round hollow metal disc will shield the RF field of the coils and inhibit production of the plasma in the chamber.
Therefore, there is a need for an improved method for delivering gas in an inductively coupled plasma processing reactor.